Our long-term goal is to develop a natural hepatic scaffold with multi-cellular cues for complete and stable maturation of stem-derived liver cells to engineer functional livers in vitro and use them for modeling liver steatosis and therapeutics. The objectives of the proposed study are to develop an organ culture system for liver engineering with induced pluripotent stem (iPS) cell-derived liver cells, and investigate its employment to understand pathogenesis, natural history and development of early detection tools and treatments for fatty liver diseases. The central hypothesis to be tested here is that the decellularized natural liver scaffold can be extensively repopulated, will provide a stable organ-like environment for the metabolic maturation of iPS derived liver cells, and may be used as an approach to induce formation of functional mini-livers using human wild type iPS cells or iPS cells after genetic engineer for fatty liver disease by knockdown of SIRT1 and/or (key gene implicated with liver steatosis formation). The rationale for the proposed research is that, once human liver tissue with multi-cellular cues can be reproducibly manufactured in vitro with normal and disease phenotypes, development of liver steatosis can be manipulated pharmacologically, resulting in new and innovative approaches to the prevention and treatment of a variety liver disease. The work described here is expected to i) generate a metabolic maturation system for human iPS cell-derived liver cells to form tissue, ii) establish human iPS cells carrying shRNA mediated conditional knockdown of SIRT1 and iii) develop a novel approach for modeling an organ-like environment to determine the role of SIRT1 in human liver steatosis or fatty liver disease. The results of this work will also have a positive impact by establishing the basis and platform for future sophisticated organ engineering techniques that incorporates several different cell types and may lead to development of entire organs in vitro, these techniques could be applied to study other liver diseases (e.g. metabolic diseases) and is expected to be a major contribution to the fields of stem cells engineering and liver steatosis.